The instant invention relates to processes for preparing water soluble and oil soluble antioxidant compositions extracted together from Labiatae herbs in a single extraction using alcohol and water, followed by a simple, yet effective, purification step that allows the separation of the water soluble antioxidative fractions containing mainly rosmarinic acid from antioxidative fractions containing mainly carnosic acid and carnosol, without cumbersome acid/base partitioning steps.
Substances that serve to protect foods from the deleterious effects of oxidation are commonly added to foods and are called antioxidants or stabilizers. These substances can be naturally or synthetically derived, although consumers generally prefer those materials from natural sources. Rosemary (Rosmarinus officinalis) has been used in culinary applications since ancient times and reports on its antioxidant activity date back to the 1950s (Chipault et al., 1956). There are over 250 reports on the potency of dry rosemary, rosemary oleoresin, rosemary extracts and the individual active antioxidant molecules in rosemary (carnosic acid, carnosol, epirosmanol, isorosmanol, methyl-epirosmanol, rosmanol, rosmanidiphenol, rosmarinic acid, rosmariquinone and ursolic acid) in various food systems (Etter, 2004). The most abundant individual antioxidant components in rosemary are the water soluble phenolic acid, rosmarinic acid, and the oil dispersible diterpenoid, carnosic acid.
Due to the high polarity of rosmarinic acid, the most common method for its extraction involves the use of water (according to U.S. Pat. No. 4,354,035), or a highly polar solvent mixture, preferably after removing the fats (also known as defatting or degreasing), de-oiling (removing aromas) or even extracting the carnosic acid and the compounds of similar polarity with a less polar solvent first, before re-extracting with a polar solvent to obtain rosmarinic acid in the water soluble fraction.
On the other hand, carnosic acid, carnosol and other rosemary ingredients of similar polarity are preferably extracted with organic solvents, less polar than water such as methanol, acetone, petroleum ether and hexane, in addition to supercritical CO2 extraction (Chen et al., 1992; Baskan et al., 2007, U.S. Pat. No. 5,256,700).
It is the aim of this invention to provide a method to extract antioxidative flavoring compositions from Labiatae plants using a “green”, that is, environmentally friendly, single step extraction, to obtain acceptable yields of both rosmarinic acid (water soluble) and carnosic acid (water soluble at high pH values, and oil dispersible). Subsequently, it is the aim of this invention to solve the problem of separating the water soluble fraction from the carnosic acid fraction, without the need of cumbersome, costly, and difficult to scale, separation and purification processing steps.
We have discovered that Labiatae herbs may be extracted with certain ratios of an ethanol/water mixture to provide both rosmarinic acid and carnosic acid in acceptable yields. The solvent of the post-extraction solution is partially distilled out to a point where, surprisingly, the carnosic acid containing fraction may be separated from the water soluble fraction (containing mainly rosmarinic acid) by simple filtration. The ethanol/water solution is distilled to decrease the pH and to decrease the relative ethanol concentration (and consequently increase the water concentration) to an ethanol level of about 0% to 35%, resulting in a concomitant gradual increase in concentration of both the carnosic acid fraction and water soluble fraction in the solution. At this point in the extraction process, the carnosic acid precipitates from the solution, whereby a carnosic acid fraction is obtained by simple filtration of the solution. The water soluble fraction comprising rosmarinic acid is retained in the solution after filtration of the carnosic acid precipitate.
Thus, the process of the instant invention provides for facile isolation of carnosic acid, which process provides an improvement over the conventional techniques for isolating carnosic acid which may encompass the cumbersome steps of adding acids/bases to transfer the carnosic acid into and out of the aqueous phase, or removing the solvent to complete dryness of the extract and then re-extracting carnosic acid with a non-polar solvent, or solvent/solvent partitioning, or adsorbing carnosic acid onto a resin then selectively extracting it with an appropriate solvent.